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Full text of "The Morphology And Evolution Of The Apes And Man"

THE MUSCULAR SYSTEM                 163
part runs from the internal tarsal ligament to the lateral tarsal raphe. Both parts are continuous, and the ciliary bundles are well marked.
The facial muscles have received considerable attention from Euge 1.141, 141a) and Sonntag {399* : and it appears that there are individual variations in the degree of subdivision.
The zygomatic mass (fig. 27.-0 consists of slips from the zygoma (zygomaticus major), malar bone and temporal fascia izygomaticus minor) and rnnsculus orbicularis oculi. These slips vary in the degree of fusion at their origins, but they all unite to form a thick bundle blending with the orbicularis oris at the angle of the mouth. Man has the best differentiated zygomaticus major.
The depressor labii inferioris (fig. 27s) arises from a variable extent of the lower border of the outer surface of the mandible* The fibres run forwards and blend with the orbicularis oris. The opposite muscles blend across the chin. Branches of the facial artery traverse it.
The triangttlaris varies in size. It emerges from the platysma and blends with the orbicularis oris.
The levator anguli oris (fig. 27s) arises from the maxilla below the infra-orbital foramen and blends with the orbicularis oris.
The levator labii superioris arises from the whole infra-orbital border of the maxilla, and is blended in the orbicularis oris with the other muscles. The most mesial fibres form the levator labii superioris alaeque nasi.
The buccinator (fig. 27B) arises from the maxilla and mandible close to the last molar teeth, and from the